If your water heater stops producing hot water after you shut the water off and turned it back on, it can feel like something serious broke. In many cases, the issue is caused by air in the lines, a safety shutoff, or a valve that wasn’t fully restored — not a failed water heater.
Most of these problems are fixable without replacing the unit.
Quick Answer:
After a water shutoff, water heaters may stop working due to trapped air, closed valves, or safety systems preventing operation. Restoring water fully, clearing air, and checking power or gas usually resolves the issue.
Why This Happens
Water heaters are sensitive to pressure and flow changes. When water is shut off, the heater may partially drain or lose pressure, which can trigger safety features or interrupt normal operation.
Common causes include:
- Air trapped in the hot water lines
- The cold water supply valve not fully reopened
- The water heater shutting down as a safety precaution
- Pilot lights going out on gas heaters
- Heating elements not activating due to lack of water flow
These issues often appear after turning your water back on after shutting it off, especially if water was restored quickly.
Step-by-Step: What to Do If Your Water Heater Isn’t Working
Step 1: Confirm Water Is Fully Restored
Before checking the heater itself:
- Make sure cold water runs normally at sinks
- Check that pressure has stabilized
If pressure is still uneven, refer back to how long it takes for water pressure to normalize after a shutoff.
Step 2: Check the Water Heater Supply Valve
Locate the cold water valve feeding the heater.
- Ensure it is fully open
- Turn it counterclockwise until it stops
A partially closed valve can prevent the heater from filling properly.
Step 3: Clear Air From the Hot Water Lines
Open a hot water faucet:
- Let it run until sputtering stops
- Wait for steady flow
Air trapped in hot lines can prevent proper heating and circulation, similar to air trapped in water pipes after a shutoff.
Step 4: Check Power or Gas Supply
For electric water heaters:
- Check the breaker
- Reset it if tripped
For gas water heaters:
- Verify the gas valve is on
- Check whether the pilot light is lit
- Follow manufacturer instructions to relight if needed
Many gas heaters shut down automatically after a pressure interruption.
Step 5: Give the Heater Time
Once water flow is restored:
- Hot water may take 30–60 minutes to return
- Larger tanks may take longer
This is normal and not a sign of failure.
What Not to Do
- Don’t turn the heater on if water flow is not restored
- Don’t assume the heater is broken immediately
- Don’t drain the heater again unless instructed
- Don’t ignore warning lights or error codes
Running a heater without proper water flow can cause damage.
When to Call a Professional
Call a plumber or technician if:
- The heater won’t refill or heat after checks
- Error codes persist
- You hear unusual noises from the tank
- There is visible leaking around the heater
If multiple fixtures are affected, the issue may be related to problems after restoring water to the house, not the heater itself.
Safety Notes
- Always restore water fully before powering a heater
- Clear air from hot lines before heavy use
- Follow manufacturer instructions for relighting
- Watch closely for leaks after restoration
Water heaters rely on proper flow to operate safely.
Common Homeowner Questions
Can a water shutoff damage a water heater?
Not usually. Most issues are temporary and related to air or safety shutdowns.
Why do I have cold water but no hot water?
The heater may not be refilled, powered, or relit yet.
How long should I wait before calling for help?
If hot water hasn’t returned after an hour and checks are complete, it’s reasonable to call.